I had a great training sortie with John Harte on Friday. We launched around sunrise and hit three other airports before returning to Detroit City (KDET) around 9:00.

Among the maneuvers was the practice emergency return to the runway. We did one of these on my first training flight in the right (primary) seat. I’ve since become pretty good at them for a greenhorn. I’ve wanted to take up a lot of cameras and film one and I got the chance on this sortie. The video starts with a landing on Runway 27L at Oakland County International Airport (KPTK). Then we power up, climb to a little over 300 AGL, pull the power, and come back to 9R.

A few weeks ago, I posted in a few social media outlets that we in the aviation community do a lot of complaining about how badly the non-aviation media screws up aviation coverage but we really don’t do much to fix it. We really ought to put together a FAQ or a wiki for the relatively few mainstream journalists who care enough to read up and get it right.

I got a lot of good feedback. Enough that I think it’s a viable idea. I haven’t decided yet whether to make it a FAQ or a wiki or something else. But I figured that I’d put together an initial entry on a topic that most non-aviation journalists seem to get wrong as an example of what I’m thinking about doing.

If you’re interested in assisting, please crop me a comment on this entry. And, if you have suggestions about this particular entry or about means to make the FAQ/wiki/whatever work, let me know those, too.

So here goes . . .

What’s a “stall?” And why does it have nothing to do with the aircraft’s engine?

The general public understands that, when a car’s engine stops running in an unplanned sort of way, that engine has “stalled.” But “stall” means something completely different in the context of aviation.

A stall in an airplane usually has nothing to do with the engine. Sure, an airplane’s engine can “stall,” but aviators usually use some other word, such as “quit” or “stop.”

Let’s talk about how an airplane stalls. Airfoils develop lift by moving through the air. Airfoils include the wings on airplanes, the rotor blades on helicopters, and lots of other things. The control surfaces on airplanes and even the propeller blades themselves are also airfoils. Heck, a barn door can be an airfoil under the right circumstances.

We’re going to talk about some specific kinds of airfoils, namely the wings on airplanes. Generally, the aircraft engine rotates the propeller, pushing or pulling the airplane through the air and creating airflow over the wings. The wings develop lift when they interrupt the air, sending some over the top and some over the bottom. The air over the wings develops something called “laminar flow,” which is a fancy way of saying that the air on both the top and the bottom of the wing moves quickly and uniformly in the area very close to the wing.

The angle of a wing as it meets the airflow is called the “angle of attack.” When you tip a wing up into the airflow – when you increase the angle of attack – more air hits the bottom of the wing and there’s a greater pressure differential. Low angles of attack are good for cruising and that’s what you see when you see an airplane overhead that’s pretty much level and is on its way somewhere. High angles of attack are good for climbing. You can see an airplane with its wings at a high angle of attack every time you go to the airport and see them taking off.

With us so far? Good!

Imagine what would happen if you increased the angle of attack a lot. Thirty or forty degrees or something like that. At some point for every wing, the airflow is simply smacking the bottom of the wing and not enough air goes over the top of the wing to keep that laminar flow. Eddies and turbulence build up on the top of the wing and the laminar flow just dissolves.

At that point, the wing won’t fly anymore. It’s not developing lift. That angle of attack for any given wing is the “critical angle of attack.” When a wing exceeds its critical angle of attack, the wing is “stalled.” When aviators talk about an airplane being stalled, they mean that the airplane’s wings have exceeded the critical angle of attack and that the wings aren’t developing lift like they otherwise might. What does that look like? The airplane’s nose is usually very high and its forward speed is very low.

Technically speaking, stalls are entirely dependent on the angle of attack of the wing. But airspeed (the speed of the airplane through the air) is a pretty good proxy for that angle of attack. The slower the airplane is moving through the air, the less air is moving over the wing to create lift. And the greater the necessary angle of attack if the airplane is to keep flying at the same altitude. So sometimes pilots talk about stalls in terms of airspeed, specifically “stall speed,” below which the airplane will stall. The slower the airspeed, the more likely it is that an airplane will stall.

Stalls can be bad if they occur when the pilot isn’t expecting it, so student pilots and experienced pilots alike practice stalling their aircraft so that they know how to recover from stalls. The private pilot practical test standards require that an applicant for a private pilot’s certificate for airplanes be able to stall an airplane – and recover – with a lot of power or with little or no power, and in turns either with or without power at bank angles of up to 20 degrees.

Stalls are bad at low altitude, such as when you’re taking off or landing. It generally takes some altitude in order to recover from a stall – about 100 feet in many aircraft in the case of a power-off stall. That’s altitude you might not have.

Stalls can also lead to other bad things. One of them is a spin. A spin happens when the airplane is stalled and “uncoordinated.” An airplane is uncoordinated with the tail is not where it’s supposed to be – when the pilot doesn’t use the rudder to keep the stalled airplane from rolling in the direction of the wing that is the most stalled. Too much rudder produces a “skid” and too little rudder produced s “slip.”

If you stall and you’re sufficiently uncoordinated, one wing or the other will drop and the airplane will start falling in a lazy spiral. The spiral will be in the direction of the wing that is the most stalled. The other wing, the one that’s less stalled, will be flying just enough to keep the rotation going. It’s called “autorotation.” Being in a spin is very unpleasant if you’re not use to it. There’s a lot of green in the windshield and the airplane is turning at an increasing rate..

Stall and spin recovery isn’t particularly difficult. The pilot pushes on the yoke or stick to decrease the angle of attack and get laminar airflow over the wings. That’s usually enough to recover from a stall that hasn’t developed into a spin. If the aircraft has begun to spin, the pilot must usually use the rudder to stop the autorotation as well.

Aerobatic pilots go up and have fun with stalls and spins. You might have seen aerobatic pilots at airshows performing maneuvers called “snap rolls,” “falling leaves,” “avalanches,” and other maneuvers with equally exciting names. These maneuvers have stalls and spins as essential elements. They look dramatic from the ground and they’re fun to do in the airplane once you’re received enough training and as long as you perform them at altitudes high enough to recover if you goof it up.

The way stalls get into the news – and the way most members of the media get the terminology wrong – is when a stall results in an accident that gets reported. As you can imagine, an accident could easily occur if you stalled an aircraft so close to the ground that you didn’t have enough altitude to recover. That’s doubly true for spins, because spins usually take something like a thousand feet in which to recover.

If a stall or spin results in an accident, it’s most often in the traffic pattern of an airport. In the pattern, aircraft are moving more slowly and are turning and otherwise maneuvering to take off from, or to land on, a runway. The most common stall or spin accident in the pattern is a spin on the turn from the base leg to the final leg. That’s a 90-degree turn that begins when the pilot is flying perpendicular to the end of the runway and the pilot turns to point the airplane at the runway in order to land. Sometimes wind or distractions cause the pilot to be further away form the final approach course than the pilot planned to be, so the pilot banks further than the pilot should or tries to increase turn rate using too much rudder (a “skid”). If the pilot allows the airplane to get too slow at this point and the airplane stalls, the uncoordinated state of the airplane can lead to a spin at low altitude.

The aviation community knows a lot about stalls and spins in the pattern. We pay a lot of attention to the accident reports so that we can learn from them. Flight instructors work hard with student pilots so that they know how important airspeed and coordination are in the pattern.

Journalists sometimes report on an accident saying that the engine “stalled” when, in fact, the airplane was stalled all right (its wings had exceeded the critical angle of attack), but the engine was just fine when the airplane interfaced with the planet. The actual event that the reporter misreported was probably an aerodynamic stall and/or spin in the pattern or on takeoff or landing. Reporters who get this wrong do aviation a disservice because each time they do it, they cause a few hundred more non-pilots to believe that general aviation aircraft are mechanically unreliable. When it was actually pilot error of some kind.

So, if you’re a member of the media and someone tells you before you go on the air that an aviation accident involved a stall, inquire further and find out whether it was an aerodynamic stall. If your source is a pilot or an aviation official, chances are good that he or she won’t use the word “stall” unless it was an aerodynamic stall. If the engine quit, they’ll usually say that the engine quit. And if you ask them to clarify, you’ll be an instant Einsetin to them because you’ll have clued them in that you recognize the difference.

If you’re a pilot or aviation official with the solemn job of briefing reporters on an accident or incident involving an aerodynamic stall, please take the time to explain what an aerodynamic stall is and point out that it has little or nothing to do with the engine.

And if you’re a member of the non-flying public, recognize what aerodynamic stalls are – that they generally have nothing to do with a powerplant or any other function of an aircraft. And that pilots train long and hard to avoid situations in which stalls occur, recognize their onset, and be always ready to recover from the rare unexpected aerodynamic stall.

Aerodynamic stalls are very rare in everyday flight operations. Unless you’re a pilot who’s training or performing aerobatics, the odds are very small that you’re ever experience one – even if you fly commercially every day of the week and on weekends, too, your whole life. They just don’t happen much.

Stalls are a natural result of the behaviors of airfoils under certain extreme conditions. Aerobatic pilots put them to use in graceful and energetic performances around the world at airshows and other events. Student pilots train to recognize them and recover from them so that they can fly safely for decades to come.

I got a call about 10 days ago from Paul Wood of the Warbird Heritage Foundation and The Hoppers. Paul asked whether I might be interested in shooting a promo video for the foundation’s A-4B Skyhawk. Not being an idiot, I said yes. After trading some dates back and forth, it turned out that Thunder Over Louisville had a slot open the next weekend. So I loaded up on Thursday afternoon and headed out for Louisville.

The Louisville show is pretty interesting. It’s one of the largest airshows in the country. The box is over the Ohio River between two bridges with a boat out in the middle marking show center. The announcers and the air boss have one of the best vantage points of any airshow in the country. It’s a balcony on the 24th floor of the Galt House hotel with a commanding view of the box. And it’s perhaps unique in that the boss is actually above many of the aircraft for non-trivial parts of the show.

I understand that the local TV stations rotate as partner stations for coverage of the show. This year, it was WDRB Fox 41 and I checked out the command center on the morning of the show. Lots of activity. The airshow started out as a way to keep the crowd occupied while it waited for the fireworks display that takes place on the river and one of the bridges. The airshow has since grown to attract as least as many people as the fireworks. WDRB had something like 10 exterior cameras to cover the show and I found that the TV coverage was really quite good. I prefer to be at close as I can get to the aircraft, but the TV coverage was good enough that I could definitely see myself watching the TV even while the aircraft were in the air.

But, like I said, I’m about being as close as possible to the aircraft. Most of the larger aircraft staged from the Kentucky Air Guard installation on the east side of Louisville International Airport. That’s where I spent the show. Ace photographer and enthusiast Lindsay Shipps joined us on the ramp to shoot stills on Friday and she shot stills from the command center downtown on Saturday.

Paul started out by doing a planeside interview. Mostly talking about the aircraft and the foundation. But we also got him talking about acro and related subjects to use for the Acro Camp movie, including having Paul trash-talk Jim Rodriguez and give us a “go fint out” for the conclusion of the film.

Then is was time to mount up and fly. I put four cameras in the aircraft. I entertained thoughts of putting a camera in the tailhook, but if was just too greasy and I wasn’t entirely sure that the camera would stay on the hook at speeds of 500 knots. But we got really good shots. This one is from the primary rear-facing camera. Others included one mounted on the other side of the dash facing mostly forward and one on the side of the ejection seat looking right.

The last camera, and I think my favorite, if the one on top of the seat. This cam has something like a half inch of clearance between the seat and the canopy. The ejection seat handle (curtain style) sticks up into the field of view, but the yellow color actually looks good in the frame and, because it tends to frame Paul’s helmet, it’s actually not that bothersome.

I gave copies of all of my Friday footage to WDRB at the end of the day and WDRB used some of it in the backgrounder material about the A-4 in Saturday’s coverage. Friday was low and overcast, but not nearly as bad as Saturday, so having some footage with the sun on the aircraft and the landscape was really cool. This shot shows shows some of the Airspeed footage on WDRB in the Heritage Room at the 123rd Airlift Wing.

I’m supposed to be getting some footage from the cameras downtown to put into the promo vieo. I should have that soon and then I’ll get to working on the video. You can expect to see it as an Airspeed episode at about the time that it goes to the foundation.

I saw a certain Taco Bell commercial and I couldn’t help but put together my own version showing, at least figuratively, what it’s like to roll into the driveway at the end of a weekend as an aviation new-media guy.

TED began in 1984 as a conference to bring together people from the fields of technology, education, and design. It has since become one of the most prestigious conferences of its kind. It’s probably most notable for its “TED Talks:” 18-minute talks on some subject by an expert with an idea worth sharing. It doesn’t matter who you are, from Mike Rowe to Sir Ken Robinson to Bill Gates to Sergey Brin and Larry Page – you stand up, make as much sense as you can for 18 minutes, then sit down. 18 minutes is just about the perfect length for such a talk. It’s long enough to lay out the basics of almost any idea, but short enough to force the speaker to state it concisely and with elegance.

Having watched TED Talks for years, I’ve come to think of them as the ultimate demonstration of the communicator’s art. If you can set heads on fire in 18 minutes, you’ve really done something. It’s a challenge that I’ve wanted for years to meet. The problem is that you don’t really go to TED with your spiel. TED comes to you and asks. [Read more...]